Abstract

The coupled ocean-atmosphere response to Indian Ocean warmth is studied. It is shown with atmospheric models that Indian Ocean warmth forces a positive polarity phase of the North Atlantic Oscillation (NAO), confirming results of previous studies. Coupled model experiments show that this NAO response forces a local air-sea feedback over the North Atlantic Ocean, which intensifies the NAO response. This enhancement is realized through a positive feedback between the NAO atmospheric circulation anomaly and a tripolar North Atlantic SST pattern, consistent with other studies on North Atlantic air-sea interactions. It is concluded that the North Atlantic and European climate response to Indian Ocean warming may be considerably greater than hitherto judged from the analyses of atmospheric model experiments alone.